Ceramic crossarm seal for gas turbine regenerators

ABSTRACT

A thin walled steel case has a ceramic shoe projecting through an opening in one side thereof. Externally facing shoulders along the longitudinal edges of the shoe bear against the edges of the case. A fibrous resilient ceramic material fills the remainder of the case and is located between the bottom of the shoe and the base of the case to adsorb deflecting forces.

United States Patent lnventor Vemulapalli D. Rno

Woodhnven, Mich.

App]. No. 872,328

Filed Oct. 29, 1969 Patented Aug. 24, 1971 Assignee Ford Motor CompanyDearborn, Mich.

CERAMIC CROSSARM SEAL FOR GAS TURBINE REGENERATORS [56] References CitedUNIT ED STATES PATENTS 3,234,999 2/1966 Atwood 277/81 X 3,273,903 9/1966Chapman et a1. 277/96 3,273,904 9/1966 Chapman et a1. 277/96 3,298,4281/1967 Bubniak 165/9 3,382,915 5/1968 Turunen 165/9 PrimaryExaminer-R0bert l. Smith AttorneysJohn R. Faulkner and Glenn S. Arendsen\\\\\I\-. \.J\\\\\ 44 1 i z PATENTED M1624 I97! 3 01 414 INVENTOR BYfmanm ATTORNEYS -section.

CERAMIC CROSSARM SEALIFOR GAS TURBINE REGENERATORS SUMMARY OF THEINVENTION Crossarm seals for gas turbine engine regenerators aresubjected to widelyvarying temperature gradients both laterally acrossthe seal and longitudinally along the seal. Coated metal seals have beenused as the crossarm and have performed satisfactorily as far asfriction and wear are concerned, but the differences in expansioncoefficients of the metal shoe and the ceramicregenerator produce forcesand distortion that lead to gas leakage.

I This invention provides a seal for use in rubbing against a ceramicregenerator that can be made of the same ceramic material as theregenerator. The rubbing shoe of the seal thus has'thermal expansioncharacteristics closely approximating the thermal expansioncharacteristics of the corresponding regenerator. In addition, the sealis capable of absorbing minor manufacturing variations between theregenerator and the engine housing. The seal comprises a'thinwalled case:member having a base and longitudinal edges folded partially back overthe base to define a longitudinal opening in one side of the casemember. A structurally integral ceramic shoe is positioned in theopening of the case member. Externally facing shoulders along thelongitudinal edges of the ceramic shoe bear against the edges of thecase member forming the opening; A resilient material is located in thecase member between the base of the .case member and the inner surfaceof the ceramic shoe where the resilient material urges the ceramic shoeout of the case so the outersurface of the ceramic shoe bears againstthe moving ceramic regenerator.

A typical case member has asubstantially rectangular. cross section witha longitudinal opening in one of the larger walls. Alternatively thecase can have a truncated triangular cross section. A groove is formedin the top of the bulkhead separating the'two gas flow passages of theengine housing and the case member canbe mounted in the groove on top ofadditional spring elements.

1 BRIEF DESCRIPTION OF THE DRAWINGS FIG; I is a plan view of a gasturbine engine showing a crossarm seal made according to this invention.

FIG. 2 is a cross-sectional view taken along line 2-2 in FIG. 1 showingaseal made with a case having a rectangular cross 'FIG.3 is across-sectional view similar to FIG. 2 of a seal case having a truncatedtriangular cross section.

'F IG. 4 is a cross section of a seal having a case made with aninverted truncated triangular section. A folded spring is locatedbetween the case edges and a ceramic shoe is mounted in the base of thetriangular case.

DETAILED DESCRIPTION The housing of a gas turbine engineis representedby numeral in FIG. 1. Housing 10 contains two semicircular gas passages12 and 14 separated substantially alonga diameter by a bulkhead 16. Ashallow groove 18 having a substantially rectangular cross section iscut into the upper surface of bulkhead l6 as shown in FIG. 2.

' A seal assembly is made by forming a thin walled case member 20 into arectangular shape having a width fitting into V groove '18. Case member20 typically ismade of a metal such as stainless steeLThe longitudinaledges 22 and 24 of case member 20 are folded partially back over itsbase 26 to define portion 34 projecting outward through opening 28. Aresilient type spring 42 and a plurality of metal L-shaped clamps 44fastened to the sides of bulkhead 16 project over the upper edges ofcase member 20 to hold the seal assembly in place in the groove. Aceramic regenerator 46 then is mounted for rotation above the sealassembly where the regenerator bears against the upper surface of shoe30. Since thermal expansion coefficients of the regenerator and the shoeare substantially equal, thermally induced dimensional changes producesimilar behavior of the regenerator and the shoe. Good contact betweenthe shoe and the regenerator is maintained throughout a widertemperature'range to insure good sealing during all phases of engineoperation. Any variations that might occur are absorbed readily by theresilient material 40 or byspring 42.

At initial installation, case 20 is moved downward in groove 18 by theforce exerted by the regenerator on the seal. Spring 42 absorbs theforce and applies a sealing load that holds the upper surface of theshoe against the regenerator. The spring urges the case upward to absorbshoe wear and also seals the area between the groove and the case.

Referring to the alternate construction shown in FIG. 3, case member 20'has the cross section of a truncated triangle with edges 22 and 24projecting upward above base 26'. The wider portion 32' of the shoe 30hasa trapezoidal cross sectionwith its angled sides corresponding to theangles of the edges 22 and 24. Narrow portion 34 of shoe 30 issubstantially rectangular and has a width corresponding to the width ofthe opening defined by edges 22' and 24. A layer of resilient material40 is positioned between the base of shoe 30 and the base of case member20' and a leaf-type spring 42 is positioned between the base of the casemember and the bottom of the groove. Clamps 44' are fastened to thesides of bulkhead l6 and have upper legs angled over the projectingedges of case 20 to hold the case in place on top of the bulkhead.

The FIG. 3 construction reduces any tendency of the ceramic shoe to tiplaterally under the forces exerted by the rotating regenerator. Broadersurface contact thus is maintained between the surface of the shoe andthe regenerator, which reduces regenerator wear.

In the more flexible alternate construction shown in FIG. 4, case member20" is an inverted version of case member 20 that has a longitudinalslot 48 cut into base 26". The ends of the case member lack both theslot 48 and opening 28" and thus connect the two sides of the casemember together. A flexible metal leaf 50 is positioned betweendownwardly facing edges 22" and 24" and lengths of wire 52 arepositioned between the shoe and the ends of the leaf to hold the leaf inposition while permitting leaf flexing. Shoe 30 has its wide portion 32"projecting upward out of the case and a narrow portion 34" locatedwithin the case. Clamps 44" fastened to the bulkhead retain the sealassembly in groove 18".

Flexing of metal leaf 50 absorbs vertical movement of shoe 34" caused bydistortion or other forces. Leaf 50 also can tilt on the bottom ofgroove 18 to absorb any distortion. In addition, the leaf seals the areabetween the seal and the housing.

Thus this invention provides a seal that has thermal characteristicssubstantially similar to the characteristics of a ceramic regenerator.The seal installation compensates for wear and readily absorbs loaddifferentials. Seals of the invention can be used at the periphery ordiameter of a rotating regenerator.

lclaim:

1. In a gas turbine engine having a housing and a rotating regeneratormounted in said housing, a seal for said rotating regenerator havinggood oxidation resistance, good dimensional stability throughout a widetemperature range, and a low coefficient of friction and low wear whenrubbing against a ceramic material, said seal comprising a thin walledcase member having a base and longitudinal edges folded partially backover said base to define a longitudinal opening in one side of said casemember,

a structurally integral ceramic shoe positioned in said opening, saidceramic shoe having externally facing shoulders along its longitudinaledges, said shoulders bearing against the edges of said case formingsaid opening, and

resilient material located in said case member between the base of thecase member and the inner surface of said ceramic shoe, said resilientmaterial urging said ceramic shoe out of said case member so the outersurface of said ceramic shoe bears against a moving ceramic material toseal the surface between the ceramic material and the ceramic shoe.

2. The engine of claim 1 in which the resilient material comprises acushion made from fibrous ceramic material.

3. The engine of claim 2 in which the case member has a substantiallytriangular cross section with one of the angles thereof being truncatedto form said opening, and the shoe member has a trapezoidal lowerportion mounted within said case, said trapezoidal lower portion beingintegral with a rectangular upper portion projecting through saidopening.

4. The engine of claim 3 comprising spring means located outside of saidcase member for maintaining contact between said ceramic shoe and saidmoving ceramic material.

5. In a gas turbine engine having a housing and a rotating regeneratormounted in said housing, a seal for said rotating regenerator comprisinga case member having a base and longitudinal edges folded over said baseto define a longitudinal opening in one side of said case member, saidcase member being mounted in a groove in said housing, and

a ceramic shoe positioned in said opening of said case, said shoebearing against said rotating re generator.

6. The engine of claim 5 comprising spring means located between saidcase and the bottom of said groove for urging said case member out ofsaid groove, said spring means maintaining said shoe in contact withsaid regenerator and sealing the area between said case and said groove.

7 The engine of claim 6 in which the spring means is a foil memberhaving its longitudinal edges retained in said case member and itscentral portion bowed away from the case member, said central portionbearing against the bottom of said groove.

8. The engine of claim 6 in which the case member has a substantiallytriangular cross section, said case being truncated across one of itscomers to form said opening, said case member mounted in said groovewith the side opposite the truncated angle facing the bottom of thegroove, and the shoe has a trapezoidal lower portion mounted within thelongitudinal edges of the case, said trapezoidal portion being integralwith a rectangular portion extending through said opening,

1. In a gas turbine engine having a housing and a rotating regeneratormounted in said housing, a seal for said rotating regenerator havinggood oxidation resistance, good dimensional stability throughout a widetemperature range, and a low coefficient of friction and low wear whenrubbing against a ceramic material, said seal comprising a thin walledcase member having a base and longitudinal edges folded partially backover said base to define a longitudinal opening in one side of said casemember, a structurally integral ceramic shoe positioned in said opening,said ceramic shoe having externally facing shoulders along itslongitudinal edges, said shoulders bearing against the edges of saidcase forming said opening, and resilient material located in said casemember between the base of the case member and the inner surface of saidceramic shoe, said resilient material urging said ceramic shoe out ofsaid case member so the outer surface of said ceramic shoe bears againsta moving ceramic material to seal the surface between the ceramicmaterial and the ceramic shoe.
 2. The engine of claim 1 in which theresilient material comprises a cushion made from fibrous ceramicmaterial.
 3. The engine of claim 2 in which the case member has asubstantially triangular cross section with one of the angles thereofbeing truncated to form said opening, and the shoe member has atrapezoidal lower portion mounted within said case, said trapezoidallower portion being integral with a rectangular upper portion projectingthrough said opening.
 4. The engine of claim 3 comprising spring meanslocated outside of said case member for maintaining contact between saidceramic shoe and said moving ceramic material.
 5. In a gas turbineengine having a housing and a rotating regenerator mounted in saidhousing, a seal for said rotating regenerator comprising a case memberhaving a base and longitudinal edges folded over said base to define alongitudinal opening in one side of said case member, said case memberbeing mounted in a groove in said housing, and a ceramic shoe positionedin said opening of said case, said shoe bearing against said rotatingregenerator.
 6. The engine of claim 5 comprising spring means locatedbetween said case and the bottom of said groove for urging said casemember out of said groove, said spring means maintaining said shoe incontact with said regenerator and sealing the area between said case andsaid groove. 7 The engine of claim 6 in which the spring means is a foilmember having its longitudinal edges retained in said case member andits central portion bowed away from the case member, said centralportion bearing against the bottom of said groove.
 8. The engine ofclaim 6 in which the case member has a substantially triangular crosssection, said case being truncated across one of its corners to formsaid opening, said case member mounted in said groove with the sideopposite the truncated angle facing the bottom of the groove, and theshoe has a trapezoidal lower portion mounted within the longitudinaledges of the case, said trapezoidal portion being intEgral with arectangular portion extending through said opening.